1. Field of the Invention
The present invention relates to a light emitting device, and more particularly relates to light emitting device which has an excitation light source, a wavelength converting member, and a light guide.
2. Background Information
Conventionally, endoscope devices, fiber scopes and the like require a light which represents a high luminance and accurate reproduction of color information.
Therefore, the use of semiconductor light emitting elements such as light emitting diode elements (LED) and laser diode elements (LD) or the like have been proposed as light sources to replace xenon lamps or the like (for instance, JP 2002-95634-A and JP 2003-515899-A).
Semiconductor light emitting elements are compact, have good power efficiency, and emit brilliant colored light. Furthermore, these elements are formed from semiconductors, so there is no concern about burning out. In particular, semiconductor lasers emit light which has extremely high-intensity compared to that of light emitting diodes, and therefore can realize light sources with excellent illumination.
Generally, in order to be able to accurately reproduce color information using a semiconductor light emitting element, light of various wavelengths must be combined to obtain a white light.
Therefore, normally a wavelength converting member made from fluorescent material and resin or the like is used in combination with a semiconductor light emitting element.
However, the light density of semiconductor light emitting elements is extremely high, so the resin and fluorescent material or the like which make up the wavelength converting member will become hot and can be degraded. Therefore, there are problems where the life of the light emitting device is shortened or the light from the semiconductor light emitting element cannot be fully released to the outside.
Furthermore, a laser diode has a peak width at half height which is narrower than a light emitting diode, so conventional endoscope devices which use a laser diode to achieve a white light source may have problems such as color variation because of the different intensities of each laser diode, and poor color reproduction. Furthermore, a conventional endoscope device requires at least three types of laser diodes, so the output from each of the laser diodes must be controlled in order to obtain a predetermined white light, and there are problems with this adjustment being difficult. Furthermore, a laser diode has a narrower viewing angle than a light emitting diode, and the light emitting intensity is extremely high from the front, and therefore, even though the light is white, there may be problems with the color changing if the laser diode shifts position even slightly.